The river EMS: processes affecting the behaviour of metals and organochlorines during estuarine mixing

Abstract

In summer 1976, measurements were made of metals and organochlorines in solution and in suspension along with studies of transport and mixing of water and particulates in the freshwater and estuarine region of the river Ems during typical neap tide conditions. During our observations a fluid mud layer occurred on the bottom. We observed some particular properties: the mean grain size was greater than in other samples, and the organic carbon content in seston was high and consequently dissolved oxygen concentrations in water were low. There was no difference in HCH contents between fluid mud-seston and other samples. Mn content in this seston was high, and its leacheable portion was the greatest in all samples. The behaviour of other metals was different: contents were lower and thier leacheable portions were also lower than in other samples. Concentrations of Cu, Zn, and Cd in solution in the mixing zone were higher than in the fresh water and marine end members, probably as a result of local land-based sources. Variations in mineral composition of suspended material in the longitudinal profile (S = 0 to 30.10 −3 were minor. Variations in metal contents of suspended matter were interpreted in terms of variations in size/density properties. A wide range of PCB components was present in solution and suspension at concentrations in the pico- to nanogram per dm 3 range.